Ester interchange reaction using a lanthanum catalyst



.thalic acid or its dimethyl ester.

.plished when we .HO(CH ),,OH, in which n is a number not less thanESTER INTERCHANGE REACTION USING A LAN THANUM CATALYST Robert MorrisCavanaugh, Wilmington, De]., and Jane Bowen Dempster, Sunbury, Pa.,assignors to E. I. du Pont de Nemonrs and Company, Wilmington, Del., acorporation of Delaware i No Drawing. Application November 15, 1954Serial No. 468,992

Claims. (Cl. 260-75) This invention relates to an improved method forthe manufacture of monomeric and polymeric esters of polycarboxyhc acidsand more which employs a novel catalyst in the reaction mixture.

This application is a continuation-in-part of our correspondingapplication Serial No. 323,148, filed November 28, 1952, for a ChemicalProcess, which in turn was a continuation-in-part of application SerialNo. 115,942, filed September 15, 1949, for a Chemical Process, both nowabandoned.

The preparation of esters of polycarboxylic acids by the reaction ofglycols with polycarboxylic acids or their alkyl esters has assumedpractical importance. An ex ample may be taken from the preparation ofethylene glycol terephthalate by the alcoholysis reaction of ethyleneglycol with dimethyl terephthalate. The ethylene glycol terephthalatemay be subsequently polymerized to form a material possessing propertiesthat adapt it for use as an industrial fiber. In effecting the foregoingalcoholysis procedures, catalysts have been sought the improvement. obect is an eifective catalytic process for the manufacture of thereaction product of ethylene glycol and tereph- Additional objects willbe disclosed as the invention is described in detail in the following.

We have found that the foregoing objects are accomreact a glycol of thegeneral formula, 2 and not greater than 10, with at least one compoundof polycarboxylic acids and the manufacture of ethylene glycolterephthalate from A still further particularly it will be employed asthe oxide, in metallic form, or as a compound of lanthanum containing aradical of a weak acid or a radical of a volatile acid. While lanthanumis particularly effective as a catalyst in the preparation of monomericethylene glycol terephthalate, it is likewise useful in thepolymerization of the monomeric material. Lanthanum may be used as thesole catalyst effectively with preparation of material free fromantimony or germanium oxides or In carrying out the process, the effectof various catalysts was determined by the following procedure,application being made here to the preparation of monomeric glycolterephthalate.

over were not allowed to exceed -75" C.; temperature during thedistillation varied in the range of -225 C. depending on the catalystand on of the distillation.

ured amount into a side diameter.

The tube was provided with a side arm for distillation purposes, and acapillary extended nearly to the-bottom known quantity of a dye, 2representing twice the amount of color in 1, etc. The same considerableexcess of ethylene glycol was used in all preparations, for example 3 or4 as limiting.

When the final stage of the process described above was carried out at265 C. the following results were obreaction. catalyst particularly inthe but, in combination with a second results are frequently obtained.The use catalyst, even better of antimony tained: a

and germanium compounds as such second catalyst is "I l particularlyeffective. It will sometimes be desirable to Hercent LaaOn .2116catalyst add the second catalyst after, the,alcoholysis reaction (theso-called first stage of the reaction) has been completed. 1, 4 Asshownin thetable, lanthanum saltscontaining a 2 4 radical of a weak acidand lanthanum salts containing a radicalof a; volatileacid are effectivecatalysts according 1 5 to thepresentinvention. The strength oii an acidis cong veniently measured by the-equilibrium constant, K, for o. 4 thedissociation of the acid in aqueous solution, Inthe V V. Y. presentiuventiomithas. been found that lanthanum salts In another set ofexperiments the temperature in the of acids Whlch h V l 1S 1555 h are fil Stage f the reaction was keptv at 275 C Addi. effective catalysts.Examples of such effective catalysts tionany, i second stage or ly i tiphase. f shown in the tableincludeithe lanthauumsalts of phthahc thereaction was discontinued after four hours to permit aC1d X fol'mlc 351dacomparison of the rapidity otthis phase of the reaction fit l z 43('K.== 10' and benzolc d as determined by the relative viscosity of thefinal poly- -s mer. This parameter, relative viscosity, is a measure ofthe degree of polymerization. For the purposes of MQIQQW B a hanum Saltsof Volatile aclds are hkgwlse this invention, the relative viscosity wasdetermined by fif ll a l i; Salts of aiclds havlng a bollmg measuring ina capillary viscometer the viscosity of: a llliaai.a mi hi li110.111.5116? l' 91391-111 09, solution of eleven g. of the polymerdissolved in 100 cc. x m es .5. 3165? catalysts S110WI1 1I1 table of themixed solvent composed of seven parts by weight l l n ha m. Salt?hydfochlol'lc acld; (B- of tri'chl'orophenol and ten parts by weight ofphenol, and )1. m g meseh 391d. a then relating the viscosity of thispolymer solution to mild 36 the viscosity of the named mixed solvent, i.e., R h?J ad a Strong aclds have 8 effiux time for the solute eral;tendency to; retard the catalytic efiect of the lan- R mti i ig tT1thanum; salts oi volatile strong acids are nevertheless e or 8 venteiiective, apparently because the free volatile acid is In theseexperiments it will be noted that in some informed and swept; out; of'the reaction mixture with the stances antimony oxide was added as anauxiliary cataeyolvedrnethanol, although this statement is not intendedSecond stage of pol- Wt.perymerization reno- Wt. percent SbiOitlon4hrs..215 0., cent of Hours required to complete based on 0.5 mm. Hgabs. Lanthanum catalysts lanthanum the first stage or alcohoi- DMTcatalyst ysis reaction ndded'as based on auxilit y Relative M catalystProduct viscosity 1 color' oi-flnal p l m Lanthanum formats 0.05 1. 0.03 1 34 Lanthanum aeetate-.-... 0. 06 1.3--. 1.5 13 Lanthanumtrifiuoraceta 0.10 1.3-- 0. 03 2. 37 anthan ,nitrate 0.075 1.4 3 13Lanthauum phthaiate 0.073 1.4 1.5 36 Lanthanum ehloride 0.063 1.7 1 14Do 0.063 1.4 a 32V Lanthanum oxide 0.03 1.5 1 14 Lanthanum benzoate-..0.10 1.5 2 41 Lead oxldeflbO) 0.01 2.1 2.5 17 Lanthanum benzene sulionat0.11 15% complete in 2 hr Lanthanum sulfate 0.052 10% compieteinzhrs-Lnnthanum oxalate 0.059 5% complete in 2 hrs (larglhpnum oxalateinsollyst after the first stage or alcoholysis reaction had beencompleted and before the second stage or the polymerization reaction wasbegun.

It, will be noted from column 2 that the lanthanum compounds have beencompared on an equal molar basis, i. e., where the lanthanum catalystcalculated as the element was equal to 0.036 mol percent of the dimethylterephthalate (DMT). The control run using lead oxide was carried out ona 0.009 mol percent basis since this was a commercially establishedprocedure. Higher amounts of lead oxide, although giving a modestincrease in rate'of reaction, are definitely unsuitable because of amarked increase in the color factor.

The foregoing tabulations show that the use of lanthanum containingmaterials is decidedly advantageous from the view point of color of thematerial after polymerization. It is definitely advantageous also withreit is known that lanthanum 'le strong acids have only a low degreeExamples shown in the table include the lanthanum salts of oxalic acid(K=6.5X10- sulfuric acid, and benzenesulfonic acid. Values for thedissociation constants given here were taken from the Handbook ofChemistry and Physics, thirty-fifth edition (1953), Chemical RubberPublishing Company, Cleveland, Ohio, page 1637.

While the lanthanum catalyst of this invention is very desirable in thepreparation of ethylene glycol terephthalate from ethylene glycol andterephthalic acid or its lower alkyl esters, it is efiective also inester exchange reactions involving other glycols and otherpolycarboxylic acids or their alkyl esters. This is illustrated by thefollowing tabulation wherein the experiments were carried out with apolymerization temperature of 265 C.

of catalytic activity.

Reactants Catalyst Percent Color Glycol Ester Ethylene glycolDimethylsebawte-i {kfiSfII :gi ljark gray Do Dlmethylterephthalate+d mehy {figfjjj 13% 21 Diethylene glycol Dimetllylterephthalaie $2 8. 1:

Ev aylene s yc +pe t s y o 11 82 :8} 5

Ethylene glycol Isophth lie ei fif f 18} 4;

DO Terephthalic acid Fail? 18% Z;

Lanthanum in the foregoing tabulation is shown to be variations may beintroduced in details of procedures, an ffective catalyst in promotingester exchange reactions 19 quantities and specific formulas ofreactants, wlthout deinvolving various glycols and polycarboxylic acidsparture from the scope of the invention We wish to be While lanthanumhas been used in the form of its made limited, therefore, only by thefollowing claims. in the examples cited in this tabulation, it may bepresent We claim also in metallic form or as a compound of lanthanum0 1. A process for the manufacture of esters of dicarcontaining aradical of a weak acid or a radical of a boxylic acids, which comprisesreacting at a temperature volatile acid The presence of a secondcatalyst along from 150 C. to about 290 C. a glycol of the general withthe lanthanum compound has been found desirable formula HO-(CH ),,OH, inwhich n is a number not in many cases, and materials containingantimony, gerless than 2 and not greater than 10, with a compoundmanium, cerium, calcium silicon, cobalt, manganese, zinc, from the groupconsisting of the dicarboxylic acids in magnesium, etc. have proveddeslrable cooperating catawhich each carboxyl group has been esterifiedby an lysts. The amount of catalyst is not a lnmting factor, alcoholcontaining not more than four carbon atoms, but generally it is founddesirable to employ an amount said reaction being carried out in thepresence of a cataof catalyst (calculated as the element) greater than0.001 lyst taken from the class consisting of metallic lanthanum molepercent of the polycarboxylic acid or its ester An lanthanum oxide,lanthanum salts of an acid having an amount of catalyst in excess of0.07 mole percent will be equilibrium constant of less than 10 andlanthanum generally unnecessary and undesirable. To obtain the salts ofan acid having a boiling point at atmospheric full activity of any givencatalyst, it should be appreciably pressure below about 100 C. solublein the reaction medium either imtially of dunng 2. The process of claimI, in which the reaction is the course of the reaction. carried out at atemperature of from 150 C. to about The glycol entering into thisreaction will be of the 230 C. so that a monomeric ester is prepared.general formula, HO(CH ),,-OH, wherenisanumber 3. The process of claim1, in which the reaction is not less than 2 and not greater than 10.Ethylene glycol carried out at a temperature of from 230 C. to about isthe preferred diol for use because of its ava1lab1l1ty 290 C. so that apolymeric ester is prepared. and the desirable products obtalned Otherglycols may 4. A process for the manufacture of an ester of terephbeemployed, however, such as diethylene glycol 2,2- thalic acid, whichcomprises reacting at a temperature dimethyl-l,3-propanediol sometimesdesignated pentafrom 150 C. to about 290 C. ethylene glycol anddiglycol, and the like. methyl terephthalate in the presence of acatalyst taken While polycarboxylic acids have been stated to be usedfrom the class consisting of metallic lanthanum lanthain the reactions,the dicarboxylic acids are the preferred num oxide, lanthanum salts ofan acid having an equilibcompounds, with terephthalic acids as thepreferred one. rium constant of less than 10 and lanthanum saltsOrdinarily the alkyl esters of such acids will be the most of an acidhaving a boiling point at atmospheric pressure desirable form for use,for example, dirnethyl terephthalbelow about 100 C. ate We find asacceptable materials also, isophthalic 5. The process of claim 4, inwhich the catalyst comacid, sebacic acid, adipic acid azelaic acid, andman prises a catalytic material taken from the class consistothers,especially in the form of their lower dialkyl esters. ing of metalliclanthanum, lanthanum oxide, lanthanum Where the term lower alkyl estersis used we intend this salts of an acid having an equilrbnum constant ofless to include only esters of alcohols containing not more than 10- andlanthanum salts of an ac1d having a bo1lthan four carbon atoms. Inaddition to dimethyl terephmg point at atmospheric pressure below about100 C., thalate, therefore, such esters as diethyl and dlbutyl and acatalytic material taken from the class of materials terephthalates arewithin the scope of this invention containing antimony, germaniumcerium, calcium, 8111- It has been found that advantageous propertiesare con, cobalt, manganese, zinc and magnesium obtained not only 1n theglycol esters formed by the re 6. The process of claim 1 in which thecatalyst comaction of single glycols and dicarboxylic acids but bycoprises lanthanum. reactions of more than one glycol or of more thanone 7. The process of claim 1 in which the catalyst comacid in the formof their esters. Blends of glycols, there prises lanthanum oxide. fore,are desirable such as ethylene glycol with diethylene 8. The process ofclaim 1 in which the catalyst comglycol, pentaglycol and the like ACldblends are llkeprises lanthanum formate. wise frequently suitable, suchas mixtures of terephthahc 9. The process of claim 1 in which thecatalyst comwith isophthahc, sebacic, azelaic, subenc, and adipic o5prises lanthanum acetate. acids, etc It will be understood that glycolesters formed 10. The process of claim 1 in which the catalyst comfromall the foregoing reactions are usually not apphcaprises lanthanumtrifluoroacetate. ble practically in their monomeric forms but that theR f r cited in the fil f this patent polymers are the final productsdesired The catalysts UNITED STATES PATENTS of the present inventlonfunction 111 the formation of both monomers and polymers as accelerantsof the reaction 19 Whmfield et a1 1949 and as materials that allow theobtaining of a substantially 2534028 Izard 1950 c 01 0pm: e product2,643,989 Auspos et al. June 30, 1953 The invention has been describedadequately in the OTHER REFERENCES foregoing. It will be understood,however, that many 16 Lel Chuk: Chem. Abs., 42, 6630-1 (1948).

1. A PROCESS FOR THE MANUFACTURE OF ESTERS OF DICARBOXYLIC ACIDS, WHICHCOMPRISES REACTING AT A TEMPERATURE FROM 150*C. TO ABOUT 290*C. A GLYCOLOF THE GENERAL FORMULA HO-(CH2)N-OH, IN WHICH N IS A NUMBER NOT LESSTHAN 2 AND NOT GREATER THAN 10, WITH A COMPOUND FROM THE GROUPCONSISTING OF THE DICARBOXYLIC ACIDS IN WHICH EACH CARBOXYL GROUP HASBEEN ESTERIFIED BY AN ALCOHOL CONTAINING NOT MORE THAN FOUR CARBONATOMS, SAID REACTION BEING CARRIED OUT IN THE PRESENCE OF A CATALYSTTAKEN FROM THE CLASS CONSISTING OF METALLIC LANTHANUM, LANTHANUM OXIDE,LANTHAMUM SALTS OF AN ACID HAVING AN EQUILIBRIUM CONSTANT OF LESS THAN10-*2, AND LANTHANUM SALTS OF AN ACID HAVING A BOILING POINT ATATMOSPHERIC PRESSURE BELOW ABOUT 100*C.